It’s been exactly 100 years since the world saw the first deadly attack with chemical weapons. The Germans deployed tons of chlorine gas on a sector of the Western front in World War I, causing 6,000 casualties. Now chlorine gas is back on the battlefield, in Syria.

Researchers in Sweden have come up with a technique to use radioactive carbon in the atmosphere, to figure out the age of unidentified dead bodies. The scientists measure levels of carbon-14 in teeth. The World's David Baron has the story.

Hillary Clinton met with her Russian counterpart Sergei Lavrov in Moscow. At a joint news conference, the two said that there has been considerable progress to reduce their nuclear arsenals. The World's Matthew Bell takes a closer look.

The Pentagon says it's expanding land and sea-based missile defense systems in and around the Persian Gulf. The moves are intended to counter what the U-S considers a growing missile threat from Iran. The World's Matthew Bell reports.

A diplomatic dispute between Teheran and Washington over a missing Iranian nuclear scientist has taken a new turn. The Iranians say he was kidnapped by the CIA. Washington says the scientist came to the US on his own free will. Marco Werman learns more.

Iran discovered a malicious computer attack that appears to target its nuclear targets. But industry insiders believe the so-called computer worm Stuxnet actually did not do what it was intended for. The World technology correspondent Clark Boyd reports.